Found: SciFi three alien races on foreign planet/moon

Read the book 15 years ago. Book tells a story about a multi-national group of humans on a space settlement mission. I'm certain that there are American and Russian members of the crew, but there could be one or more additional groups as part of the coalition. I believe the settlement party arrives in one large space vessel, but I could be wrong. I remember that there were three alien races. One were balloon like aliens that floated in the sky; one race lived on the surface; one mostly lived burrowing underground. The settlement might've still had contact back to planet earth and were influenced by earth politics. It's revealed that the Russians have brought materials to assemble a nuclear bomb as part of the space ship. I don't remember how the plot resolves, but I know that communication is severed between the colonized planet/moon and the humans there begin a new civilization together with the aliens. The balloon aliens rain down a substance which causes a sensation of ecstasy like a drug. I can't remember much else.

May have been marketed for young adults (I found it in a school library) but the content was mature at times.

Probably Jem by Frederik Pohl. There were two or three competing expeditions from Earth, which was divided into blocs of oil-exporting countries, food-exporting countries, and people/laborer-exporting countries.

Seconding Jem. If it helps, Carl Sagan makes an appearance as a minor character.

Thank you! I think this is it!